Recent experimental evidence supports a role for AMPA/KA-type glutamate receptors in mediating ischemic neuronal death, such as occurs in stroke. Free radicals have also been implicated in the injury process that leads to ischemic cell death. The main objective of this proposal is to determine the involvement of free radical formation in AMPA/KA receptor- mediated neuronal death in oxygen-glucose deprivation in vitro and ischemic brain injury in vivo. The central hypothesis to be tested is that generation of oxygen free radicals contributes to AMPA/KA receptor- mediated neuronal death in oxygen-glucose deprivation in vitro and ischemia/reperfusion in vivo. Three specific aims and related research plans are directed at testing this hypothesis. The involvement of free radicals in AMPA/KA receptor-mediated cell death will be assessed in oxygen-glucose deprivation in vitro using mouse brain cortical cultures, and in two in vivo ischemia models (rat global ischemia and focal ischemia). In most experiments, NMDA receptors will be blocked to 'unmask' the contribution of AMPA/KA receptors. Production of free radicals will be measured using state-of-the-art methods for detecting free radicals, such as Electron Spin Resonance (ESR), and salicylate trapping/HPLC for detection of hydroxyl radical. Trapping agents (spin- traps for ESR or salicylate) will be delivered to the cells by microdialysis (in vivo) or by direct application to cells (in vitro). Protection by anti-oxidants/radical scavengers against the AMPA/KA receptor-mediated component of oxygen-glucose deprivation injury in vitro and ischemic injury in vivo will also be examined. Clarifying the sources of free radicals and the events that trigger their production may assist in the development of improved therapy for CNS ischemia.